US3376229A - Synthetic detergent bar - Google Patents

Description

Unite ABSTRACT OF THE DISCLOSURE An improved detergent-containing hand bar containing isethionate esters, soaps and fatty acids as the minor ingredients. The invention provides a minor amount of unesterified isethionate to be used as a firming agent.

This invention relates to a detergent bar having superior use properties and containing an acyl isethionate as the principal detergent component together with supplemental detergent, binder and plasticizer components.

The formulation of a bar or cake competitive with soap, yet composed entirely or predominantly of synthetic detergents, presents many problems which are quite different from the formulation of granulated or liquid synthetic detergent compositions. Nonstop detergents do not have the unique physical properties of soap which so adapt the latter material for use in bar form.

The requirements for a good toilet soap bar are well known. Such a bar should have good lathering properties in hot or cold Water, in hard or soft water, the skin should not be left feeling sticky or itchy, the bar itself should have a good feel and slip, the bar must be mild and nonirritating and the detergency should be good, so that the skin will be cleansed readily in the presence of oil.

A detergent bar having these desirable properties is disclosed in United States Patent No. 2,894,912 to Robert C. Geitz. The principal components of a detergent bar com bining the above-mentioned use properties are:

Water-soluble alkali metal detergent salts of esters of isethionic acid with mixed fatty acids At least one water-soluble sudsboosting detergent salt From 30% to 70%.

From 2% to Water From 1% to 9%. Water-soluble higher fatty acid soap From 2 /2% to about Higher fatty acid having from 12-25 carbon atoms From about 10% to about 40%. pH of 10% solution at C. Between about 6 and about 8.

Geitz discloses that generally about 2%.% soap is required to prevent cracking in a detergent bar of the above description. However, the present invention is not limited to use in connection with detergent bars containing at least 2 /2 soap.

The foregoing composition may tend to be undesirably soft, especially when more than about 4% to 5% Water is present. Such amounts of water, or even larger amounts of Water, Will commonly be present in the detergent mixture as a result of water present in the various ingredients employed therein. Partially to avoid this problem in processing blends of ingredients having the above composition, the blend may be heated to a temperature above about the boiling point of water in order to reduce the water content to a reasonable value, in the order of 4% to 5%. While theoretically substantially all of the Water could be removed in this manner, to do so is impractical in the commercial preparation of detergent bars.

States Patent 0 According to the present invention, it has been found that, 'by incorporating up to about 17% of unesterified water-soluble alkali metal isethionates in a bar of the above description, a bar of improved firmness can be obtained. The improved firmness is of particular importance to improve the ploddability of detergent compositions of the above general description, and to facilitate operations such as milling, stamping, and the like.

The ingredients which may be used in the above formulation are fully described in the Geitz Patent No. 2,894,912 mentioned above. Briefly summarized, these are as follows:

The acyl isethionate which is employed can be defined by the following formula:

Where R is a mixture of aliphatic hydrocarbon radicals of fatty acids having from 6 to 18 carbon atoms and an iodine value of less than about 20, and M is an alkali metal cation such as sodium or potassium. The iodine value of the mixed fatty acids is the average value of the mixture and is measured on the mixture.

The number of carbon atoms of the acids comprising the R radical is important. Preferably, acids having a major portion of C and C acids should be employed, and the mixture should contain generally less than about 25% of acids containing from 6 to 10 carbon atoms.

It is desired that the fatty acids should be mostly saturated. The iodine value of the mixture should preferably be less than 20.

Such acid mixtures can be made up synthetically but they are conveniently available as the mixed fatty acids derived from coconut oil, palm kernel oil (hydrogenated 0r unhydrogenated), babassu oil, and ouri curi oil. Fatty acids derived from petroleum may also be used, the acids derived from the Koch or Oxo processes or from alpha olefins being typical. For best l'athering properties, it is preferred that the detergent should not contain more than about 30% or 40% of fatty acids having 16 or more carbon atoms, particularly the saturated acids such as palmitic and stearic acids.

The amount of acyl isethionate may range from 30% to based on the active detergent, by weight of the nonsoap bar. In order to assure that lime soap curds will not be formed, generally at least 40% and preferably in excess of 48% of the nonsoap bar should be the acyl isethionate. For economic reasons, it will be preferred that the amount of acyl isethionate should not exceed about 53%.

Suds-boosting detergents which can be used are the higher aliphatic alcohol sulfates, the alkyl-aryl sulfonates, and the higher aliphatic fatty acid taurides, particularly the fatty acid amides of N-methyl taurine, or a mixture of any two or more of these detergents. The alkyl-aryl sulfonates have the best suds-boosting properties and are preferred.

These compounds can be described by the following general formulae:

R-SOJOM U SO cation of an organic amine base such as triethanolamine, triisopropanolamine, diethanolamine and monoethanolamine, and R is hydrogen or a lower alkyl radical of up to five carbon atoms, such as methyl, ethyl, butyl and pentyl.

Alkyl-aryl sulfonates are a preferred class of sudsboosters. These may be either the phenyl polypropylene sulfonates in which the polypropylene radical (R in the above general formulae) has a molecular weight corresponding to from about 12 to about 15 carbon atoms or the linear alkyl benzene sulfonates, the latter having a desirable biodegradability. Also useful are the sodium and potassium keryl benzene sulfonates, sodium nonyl benzene sulfonate, potassium nonyl toluene sulfonate, sodium dodecyl toluene sulfonate, potassium dodecyl benzene sulfonate and sodium ethyl hexyl benzene sulfonate.

Typical alkyl sulfates are sodium lauryl sulfate, sodium palmityl sulfate and triethanolamine myristyl sulfate.

Typical fatty acid taurides are sodium palmityl N- methyl tauride, sodium oleyl N-methyl tauride, sodium tauride, sodium oleyl tauride, and sodium coconut oil fatty acids N-methyl tauride.

The amount of supplemental suds-boosting synthetic detergent or detergent mixture may range from 2% to 10%. Generally, increasing the amount from 5% to does not lead to appreciably improved sudsing. Therefore, the optimum amounts are between about 2% and about 5%.

The aliphatic carboxylic acids, which are employed as binder-plasticizers in the free acid form, have a relatively high molecular weight to take advantage of the waxy and lubricant characteristics of such acids. The acids may be saturated or unsaturated and may be straight chain or branched chain, and have from about 12 to about carbon atoms. The unsaturated mixtures should have an iodine value of less than about 20. The following are exemplary of the acids which may be used: lauric acid, lignoceric acid, myristic acid, arachidie acid, behenic acid, palmitic acid, stearic acid, oleic acid, isooleic acid, octadecenoic acid, ricinoleic acid, erucic acid, eleostearic acid, palmitoleic acid, linoleic acid, dihydroxystearic acid, and the mixed higher fatty acids derived from naturally-occurring oils and fats such as coconut oil, lard, tallow, palm kernel oil, myristic fat, stearin, seed fats, linseed oil, cottonseed oil, fish oils, whale oil, tall oil, rosin, greases, soybean oil, olive oil, babassu oil, castor oil, peanut oil, and mixtures of any of such acids. Synthetic acids, derived from petroleum by the Koch or 0x0 processes or from alpha olefins may also be used.

The preferred binder-plasticizer is a mixture of the 16 carbon and 18 carbon saturated fatty acids, i.e., palmitic and stearic acids, in a ratio of between about :70 and 70:30 by weight. Commercially available triple pressed stearic acid and its mixtures with palmitic acid are especially preferred binder-plasticizers.

A solid polyethylene glycol can be substituted for a part of the acid binder-plasticizer. The polyethylene glycol makes plodding and stamping of the bar easier, and improves the feel of the bar in very cold water. A mixture of 5% polyethylene glycol and 20% triple-pressed stearic acid is satisfactory. However, because these materials are water-soluble, their use tends to make the bar more soluble in water, leading to excessive wasting, and therefore the amount of this material would be kept at a minimum. No more than 20% by weight of the nonsoap bar should be a solid polyethylene glycol.

Generally, the amount of aliphatic carboxylic acid may be between about 10% and about of the finished bar (by weight). Preferably, however, the bar will contain between about 18% and about 24% by weight of the carboxylic acid.

The aliphatic carboxylic acid serves as the principal plasticizer in the nonsoap bars of the invention. Water is used as a supplemental plasticizer. Bars may be made without water. However, to improve plasticity and reduce brittleness so that the bars have little or no tendency to shatter on impact, water should be present. Too much water will make the bar too sticky to process, while if too little is used, the bar will become hard and brittle shortly after being stamped. The amount of water may range up to 9%, preferably from 3.5 to 7%, of the finished bar, depending somewhat upon processing limitations in the available equipment. The amount of water is closely correlated with the plodding conditions.

In bars prepared in accordance with the Geitz patent, between about 2 /z% and about 25% of a soap of a fatty acid should also be provided. As already noted above, however, the present invention is not limited to the preparation of soap-containing detergent bars.

The soaps appropriate for use in detergent bars according to Geitz are the well-known alkali metal salts of fatty acids, i.e., soaps derived from naturally-occurring fats and oils such as coconut oil, palm oil, palm kernel oil, tallow, hydrogenated tallow, hydrogenated lard, hy drogenated white grease, stearic acid, palmitic acid,.hydrogenated palmitic acid, hydrogenated oleic acid, and lauric acid. From 10% to 18% of soap by weight will improve sudsing as well as the bar texture or feel.

The total amount of soap added will depend to a certain extent upon the amount of the fatty acid binder. There should be between about 2 /2 to 6 parts by weight of soap for each 10 parts of fatty acid binder. The preferred range stated 'by Geitz is between about 4 and 5 parts of soap for each 10 parts of fatty acid binder.

In accordance with the present invention, it has been found that the presence of a free isethionate will noticeably improve the hardness and processing characteristics of detergent bars of the foregoing general description. As little as about 2 /2% of free isethionates in the detergent bar (based on the finished weight thereof) will provide a substantial from about 4% to about 17% isethionates should be present. Most commercial preparations of the isethionate esters will contain some small amount of free isethionates and this should be taken into consideration as contributing to improved plodding characteristics. For best results, additional free isethionate will be needed, and at least 1% or more (based on the weight of the finished composition) of free isethionate should be added.

In this invention, an adequate improvement in processing characteristics will normally be obtained when the free isethionate content is between about 4% and about 7% by weight of the finished bar.

In general, the same class of isethionates which may be employed for the preparation of the principal detergent active ingredient is suitable for the purpose of improving the hardness of the detergent bar. These are specifically the alkali metal salts of isethionic acid. Sodium isethionate is particularly valuable for commercial purposes because it is readily available. Potassium isethionate may also be used. The free isethionate used will most conveniently be the same isethionate which is esterified to form the principal detergent active ingredient, a different isethionate from the above-mentioned class may be used.

It is well known in the art that isethionate esters can be prepared by reacting the free isethionate with a fatty acid chloride, this method being well-established commercially for the preparation of the isethionate esters. Commonly, this process will leave a sufficient amount of free isethionate in the isethionate ester so that when the ester is used in the manufacture of a detergent bar containing approximately isethionate ester, the resulting bar will contain approximately 2.5% free isethionate. This amount will contribute to the desired plodding characteristics.

It has been proposed more recently to manufacture the isethionate esters by a direct esterification reaction. The direct esterification process, however, leaves a smaller residue of unreacted isethionate in the reaction product.

improvement in the plodding characteristics. In the preferred embodiments, however, generally Accordingly, when such a reaction product is employed in the manufacture of detergent bars to yield a bar containing approximately 50% isethionate ester, there will be only about 1.9% free isethionate in the bar. This reduction in free isethionate content is sufficient to cause a noticeable deterioration in the plodding properties of the resulting bar. To overcome this deficiency at least about 1% additional isethionate should be provided in the detergent bar.

In detergent bars of the foregoing description, the presence of at least from about 2 /2% to 4% free isethionate will produce a bar of noticeably improved hardness. Hardness of itself is an important factor in providing desira'ble processing characteristics. It is not, however, a reliable guide as to all of the desirable processing characteristics. Noticeable distinctions may be observed between bars of equal hardness. Among the other factors of particular importance in operations such as extrusion, milling, and stamping, is the property of slip. The detergent material must exhibit a low degree of friction with respect to the metallic surfaces of the processing equipment with which it comes into contact so that it will flow smoothly without causing excessive back pressure or undesired surface defects.

It is because of the necessity of obtainingdesira'ble slip properties that the presence of a free isethionate is particularly valuable. Bars of increased hardness can be made by other methods. Thus, for instance, hardness may be increased by decreasing the amount of plasticizer (i.e., the free higher fatty acid) and substituting therefor an inert filler such as sodium chloride. Alternatively, hardness may be increased by decreasing the amount of water present in the detergent bar. These alternatives, while increasing the hardness of the bar do not provide the improved processing characteristics which will be provided by the presence of free isethionates.

For a further understanding of this invention reference may be had to the following examples:

EXAMPLE 1 A detergent bar was prepared .by the following procedure:

(a) Add free fatty acids to a mixing vessel and melt these acids by heating.

(b) Add sodium acyl isethionate (prepared by the direct esterification process).

(c) Add free sodium isethionate, fatty acid soaps, mixed polypropylene benzene sulfonates in which the polypropylene contains between about 12 and 15 carbon atoms, Water and miscellaneous ingredients.

((1) Mix the above ingredients at about 230 F. for a period of about 15 minutes.

(e) The mixed mass is dumped onto chilled rolls where it is cooled to about 100 F.

Thereafter the chilled material is milled, plodded, and stamped to form bars.

Fr 'the control run no sodium isethiona te was added.

Using the foregoing procedure, three batches of bars were prepared containing varying amounts of free sodium isethionate as follows:

Formulation 1 2 3 Fatty acid isethionates 49. 00 49.00 49.00 Mixed polypropylene benzene suifonates.- 2. 03 2. 03 2. 03 Mixed palmitic and stearic acids and fatty acids from fatty acid isethionate 20. 00 20. 00 20. 00 Mixed palmitie and stearic acids added. 10. 50 7. 40 5. 40 Sodium isethionate from fatty acid isethionates l. 90 1. 90 1. 90 Sodium isethionate added 0 3. 00 5. 00 Soap: 80/20 tallow/coco 10. 00 10. 00 10. 00 H5O 4. 75 4. 75 4. 75 Miscellaneous 1. 82 1. 82 1. 82 Hardness:

Temperature F 105 105 111 Penetration 1 (in mm.) 100 23 50 1 The firmness of the plodded log was measured by the use of a penetrometer. A fixed weight of 1 pound falls through a distance of 1.5 and the depth of penetration into the log is measured. The higher the penetrometer reading, the softer the log.

In formulations 2 and 3 above, containing respectively 4.9 and 6.9% sodium isethionate, the plodding characteristics, milling characteristics, and stampability were noticeably improved.

EXAMPLE 2 Isethionates may be used as hardening agents for the purpose of improving processing characteristics in conjunction with other hardening agents.

A detergent bar was prepared by the following procedure:

(a) Add free fatty acids to a-mixing vessel and melt these acids by heating.

(b) Add sodium acyl isethionate (prepared by the direct esterification process).

(c) Add free sodium isethionate, fatty acid soaps, mixed polypropylene benzene sulfonates in which the polypropylene contains between about 12 and 15 carbon atoms, water, sodium stearate and miscellaneous ingredients. Sodium stearate was added as a second hardening agent.

(d) Mix the above ingredients at about 235 3. period of about 15 minutes.

(e) The mixed mass is dumped onto chilled rolls where it is cooled to about F.

Thereafter the chilled material is stamped to form bars.

Using the foregoing procedure, four batches of bars were prepared containing varying amounts of free sodium F. for

milled, plodded, and

isethionate as follows:

Formulation 4 5 6 7 Fatty acid isethionates 51.10 61. 10 51. 10 51. 10 Mixed polypropylene benzene sulfonates..... 2.03 2.03 2. 03 2. 03 Mixed palmitic and stearic acids and fatty acids from fatty acid isethionate 15. 78 15. 78 15.78 15. 78 Mixed paimitic and stearie acids added 10. 70 5. 70 0. 70 0 Sodium isethionate from fatty acid isethionates 1. 90 1. 90 1. 90 1.90 Sodium isethionate added. 0 5.00 10.00 15. 00 Soap: 80/20 tailow/coco 8 0 50 5 4. 20 H2 4. 75 4. 75 4. 75 4. 75 Misceiianeous 2. 24 2. 24 2. 24 2. 24 Hardness:

Temperature F 101 102 104 105 Penetration 1 (in mm.) 46 26 19 23 1 The firmness of the plodded log was measured by the use of a pene trometer. A fixed weight of 1 pound falls through a distance of 1.5 and the depth of penetration into the log is measured. The higher the penetroineter reading, the softer the log.

In formulations 5, 6 and 7 above, containing respectively 6.9, 11.9 and 16.9% sodium isethionate, the plodding characteristics, milling characteristics, and stampability were noticeably improved.

Examples 1 and 2 may be repeated substituting about 5% polyethylene glycol having a molecular Weight of 4,000 for a portion of the mixed fatty acids employed therein. Likewise, potassium isethionate may be substituted for the sodium isethionate. In each case similar results will be obtained.

We claim:

1. A detergent bar consisting essentially of from 30% to 70% of water-soluble alkali metal detergent salts of esters of isethionic acid with mixed aliphatic fatty acids having from 6 to 18 carbon atoms having an iodine value of less than 20 and containing up to about 25% fatty acids having from 6 to 12 carbon atoms, from 2% to 10% of at least one water-soluble suds-boosting detergent salt selected from the group consisting of alkali metal and organic amine higher aliphatic fatty alcohol sulfates, alkyl aryl sulfonates and higher aliphatic fatty acid ta-urides, from about 1% to about 9% water, from about 2.5% to about 25 of water-soluble higher fatty acid soaps, from about 10% to about 40% of at least one higher fatty acid having about 12 to about 25 carbon atoms as a binder and plasticizer, and from about 4% to about 17% of unesterified water-soluble alkali metal 1 For the control run no sodium isethionnte was added.

salts of isethionic acid, said bar having a -pH between about 6 and about 8 when measured as a 10% aqueous solution of the bar composition at 35 C.

2. A detergent bar according to claim 1 containing between about 4% and about 7% of unesterified watersoluble alkali metal salts of isethionic acid.

3. A detergent bar according to claim 1, wherein up to about 20% by weight of the fatty acid is replaced with a solid polyethylene glycol.

4. A detergent bar according to claim 1 containing between about 18% and about 24% of fatty acids having between about 12 and about 25 carbon atoms.

5. A detergent bar according to claim 1 containing between about 3.5 and about 7% water.

6. A detergent bar consisting essentially of from about 48% to about 53% of water-soluble alkali metal detergent salts of esters of isethionic acid with mixed aliphatic fatty acids having from 6 to 18 carbon atoms having an iodine value of less than 20 and containing up to about 25% fatty acids having from 6 to 12 carbon atoms, from 2% to about 5% of an alkyl aryl sulfonate, from about 3.5% to about 7% water, from about 10% to about 18% of a water soluble higher fatty acid soap, from about 18% to about 24% of at least one higher fatty acid having from about 12 to about 25 carbon atoms as a binder and plasticizer, and from about 4% to about 7% of unesterified water-soluble alkali metal salts of isethionic acid, said bar having a pH between about 6 and about 8 when measured as a 10% aqueous solution of the bar composition at 35 C.

7. A detergent bar according to claim 6 containing from about 48% to about 53% of the ester of sodium isethionate and fatty acids derived from coconut oil.

8. A detergent bar according to claim 6, wherein said binder and said plasticizer is a saturated higher fatty acid having from about 16 to about 18 carbon atoms.

9. .A detergent bar according to claim 6 containing from about 4% to about 7% unesterified sodium isethionate.

References Cited UNITED STATES PATENTS 2,894,912 9/1954 Geitz 252-121 FOREIGN PATENTS 1,111,617 7/1961 Germany.

421,527 9/ 1933 Great Britain. 560,328 7/1958 Canada.

LEON D. ROSDOL, Primary Examiner.

B. BETTIS, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 76,229 Dated April 2 1968 Inventor(s) Robert A. Haass and Vincent Lamberti 7 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, line 6, change 12" to l0.

Claim 6, line 6, change "12" to lO-.

Signed and Scaled this sixteenth Day Of September 1975 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN 'lllesling Ojfirer (nmmlssiuncr 0] Palents and Trademarks